It’s an everyday intuition shared by millions, perhaps billions of people, now validated by research: Overheard cellphone conversations are very distracting.

According to a new study, listeners notice those conversations more than dialogue between two people. It’s a seemingly involuntary response. There’s just something attention-demanding about hearing one person on a phone.

The next question is whether those demands affect how we think, even pulling a curtain of cognitive impairment across a cellphone-suffused civilization.

“We thought it would be interesting to see, since people consider them annoying and distracting, whether they have any impact on attention and memory,” said Veronica Galvan of the University of San Diego, lead author of findings published March 13 in PLoS One.

As context, Galvan’s paper gives, in numerical and analytical form, statistics which are felt every time a nominally quiet place hums with one-sided chatter: Americans spend something like 2 trillion minutes on cellphones each year, forming such deep emotional attachments to their devices as to have trouble turning them off.

Yet despite the ubiquity of cellphones, especially in crowded, public spaces, and the wealth of research on how talking on one is quite distracting, relatively little research exists on the effects of overhearing conversations. An earlier study observed people performing cognition-testing tasks while overhearing recorded conversations, and found evidence of distraction, but people knew they were being tested. Galvan wanted to investigate effects in a more realistic setting.

To that end, she and colleagues recruited 164 undergraduate students into what was supposedly a straightforward cognition study, with students asked to solve anagrams displayed on a computer screen. As they worked, a scripted conversation took place outside the room: Either a person on a cellphone, two people speaking normally, or two people of whom one spoke very quietly, mimicking a phone conversation’s dynamics.

'I wouldn't be surprised if you saw larger memory effects in other generations.'

How students reacted to the conversation was the real test. After finishing the anagrams, they were asked to recall certain words or phrases from the conversations. Students remembered the one-sided dialogue best, suggesting they’d paid more attention to — and been more distracted by — those conversations.

Alternatively, the one-sided conversations could have had a stimulating effect, actually improving student memory. That can’t be ruled out, said Galvan, but in light of other cellphone distraction research, she considers it unlikely.

In that earlier study of overheard conversations, the researchers linked the distraction to the cognitively unpredictable nature of what they called “halfalogues.” When hearing a one-sided conversation, our minds may automatically try to fill in the blanks. At a subconscious level, said Galvan, listeners might be trying to figure out, “Why are they saying that? Where does it come from? What are they responding to? That’s the distracting part.”

As for whether distraction resulted in cognitive impairment, though, there was no evidence. Regardless of the conversations they heard, students solved the anagrams at consistent rates. This could suggest that one-sided conversations, even if they’re distracting, don’t make much real-world difference.

Alternatively, solving anagrams is an easy thing to do, even when distracted. Effects of halfalogues on memory could become pronounced on more complicated tasks, such as reading or writing. According to cognitive load theory, minds can handle only so many streams of information before limits are reached and performance falters. That’s what makes multitasking so challenging.

“Our research is related to multitasking,” said Galvan. “It’s intriguing to me that people might perform better if there were areas where conversations are limited.”

One caveat is that the study involved college students, and predominantly female and Caucasian students at that. The findings were replicated in a similar group, but other demographics remain to be tested.

“I wouldn’t know about how other groups might be affected differently,” she said, “but I believe there’s research out there indicating that older people might be more annoyed. I wouldn’t be surprised if you saw larger memory effects in other generations.”

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